An exception is an occurrence in an application process that requires deviation from the program's normal flow.

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187
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9answers
14k views

Why do many exception messages not contain useful details?

It seems there is a certain amount of agreement that exception messages should contain useful details. Why is it that many common exceptions from system components do not contain useful details? A ...
113
votes
26answers
24k views

Are null references really a bad thing?

I've heard it said that the inclusion of null references in programming languages is the "billion dollar mistake". But why? Sure, they can cause NullReferenceExceptions, but so what? Any element of ...
93
votes
8answers
18k views

Exceptions: Why throw early? Why catch late?

There are many well-known best practices about exception handling in isolation. I know the "do's and don'ts" well enough, but things get complicated when it comes to best practices or patterns in ...
71
votes
12answers
8k views

I've been told that Exceptions should only be used in exceptional cases. How do I know if my case is exceptional?

My specific case here is that the user can pass in a string into the application, the application parses it and assigns it to structured objects. Sometimes the user may type in something invalid. ...
69
votes
5answers
7k views

How to write a good exception message

I'm currently doing a code review and one of the things I'm noticing are the number of exceptions where the exception message just seems to reiterate where the exception occurred. e.g. throw new ...
64
votes
8answers
14k views

Defensive Programming vs Exception Handling?

I'm working through the book "Head First Python" (it's my language to learn this year) and I got to a section where they argue about two code techniques: Defensive coding vs Exception handling. Here ...
64
votes
7answers
67k views

Why use try … finally without a catch clause?

The classical way to program is with try ... catch. When is it appropriate to use try without catch? In Python the following appears legal and can make sense: try: #do work finally: #do ...
52
votes
9answers
6k views

Throw exception or let code fail

I am wondering if there are any pros and cons against this style: private void LoadMaterial(string name) { if (_Materials.ContainsKey(name)) { throw new ArgumentException("The ...
52
votes
4answers
29k views

Is it better to use assert or IllegalArgumentException for required method parameters?

In Java, which is more highly recommended, and why? Both types will throw exceptions, so in that regard handling them is the same. assert is slightly shorter, but I'm not sure how much that matters. ...
51
votes
8answers
21k views

Return magic value, throw exception or return false on failure?

I sometimes end up having to write a method or property for a class library for which it is not exceptional to have no real answer, but a failure. Something cannot be determined, is not available, not ...
49
votes
12answers
29k views

Is it good practice to catch a checked exception and throw a RuntimeException?

I read some code of a colleague and found that he often catches various exceptions and then always throws a 'RuntimeException' instead. I always thought this is very bad practice. Am I wrong?
45
votes
14answers
30k views

Is using nested try-catch blocks an anti-pattern?

Is this an antipattern? It is an acceptable practice? try { //do something } catch (Exception e) { try { //do something in the same line, but being less ambitious ...
44
votes
7answers
22k views

Why is there no 'finally' construct in C++?

Exception handling in C++ is limited to try/throw/catch. Unlike Object Pascal, Java, C# and Python, even in C++ 11, the finally construct has not been implemented. I have seen an awful lot of C++ ...
43
votes
20answers
12k views

Is it ever ok to have an empty catch statement?

I thought about it and could not come up with an example. Why would somebody want to catch an exception and do nothing about it? Can you give an example? Maybe it is just something that should never ...
41
votes
10answers
5k views

Why are exceptions considered better than explicit error testing? [duplicate]

Possible Duplicate: Defensive Programming vs Exception Handling? if/else statements or exceptions I often come across heated blog posts where the author uses the argument: "exceptions vs ...
41
votes
8answers
4k views

Should I throw an exception in case of a meaningful value outside of the range or handle it myself?

I have written a struct that represents latitude/longitude coordinates. Their values range from -180 to 180 for longtitudes and 90 to -90 for lattitudes. If a user of that struct gives me a value ...
40
votes
11answers
6k views

Are error variables an anti-pattern or good design?

In order to handle several possible errors that shouldn't halt execution, I have an error variable that clients can check and use to throw exceptions. Is this an Anti-Pattern? Is there a better way to ...
40
votes
11answers
16k views

Are there any real-world cases for C++ without exceptions? [closed]

In When to use C over C++, and C++ over C? there is a statement wrt. to code size / C++ exceptions: Jerry answers (among other points): (...) it tends to be more difficult to produce truly tiny ...
39
votes
9answers
16k views

Are exceptions as control flow considered a serious antipattern? If so, Why?

Back in the late 90's I worked quite a bit with a code base that used exceptions as flow control. It implemented a finite state machine to drive telephony applications. Lately I am reminded of those ...
39
votes
12answers
3k views

Why are errors named as “Exception” but not as “Error” in programming languages?

I've been thinking about that for quite a while actually. I am not a native english speaker myself but still I have years of programming experience and I always asked me this. Why is it named as ...
39
votes
7answers
3k views

Are there legitimate reasons for returning exception objects instead of throwing them?

This question is intended to apply to any OO programming language that supports exception handling; I am using C# for illustrative purposes only. Exceptions are usually intended to be raised when an ...
38
votes
9answers
6k views

Should I accept empty collections in my methods that iterate over them?

I have a method where all logic is performed inside a foreach loop that iterates over the method's parameter: public IEnumerable<TransformedNode> TransformNodes(IEnumerable<Node> nodes) { ...
37
votes
3answers
12k views

Why are exception specifications bad?

Back in school some 10+ years ago, they were teaching you to use exception specifiers. Since my background is as one of them Torvaldish C programmers who stubbornly avoids C++ unless forced to, I only ...
36
votes
11answers
19k views

Is catching general exceptions really a bad thing?

I typically agree with most code analysis warnings, and I try to adhere to them. However, I'm having a harder time with this one: CA1031: Do not catch general exception types I understand the ...
36
votes
4answers
4k views

Python Forgiveness vs. Permission and Duck Typing

In Python, I often hear that it is better to "beg forgiveness" (exception catching) instead of "ask permission" (type/condition checking). In regards to enforcing duck typing in Python, is this try: ...
35
votes
5answers
3k views

Why are brackets required for try-catch?

In various languages (Java at least, think also C#?) you can do things like if( condition ) singleStatement; while( condition ) singleStatement; for( var; condition; increment ) ...
35
votes
6answers
11k views

Workaround for Java checked exceptions

I appreciate a lot the new Java 8 features about lambdas and default methods interfaces. Yet, I still get bored with checked exceptions. For instance, if I just want to list all the visible fields of ...
34
votes
4answers
17k views

Why do iterators in Python raise an exception?

Here's the syntax for iterators in Java (somewhat similar syntax in C#): Iterator it = sequence.iterator(); while (it.hasNext()) { System.out.println(it.next()); } Which makes sense. Here's ...
33
votes
8answers
4k views

Are exceptions an OOP concept?

Having read a post yesterday, I realized I did not know much about the origin of exceptions. Is it an OOP related concept only? I tend to think it is, but again there are database exceptions.
32
votes
6answers
9k views

Why design a modern language without an exception-handling mechanism?

Many modern languages provide rich exception handling features, but Apple's Swift programming language does not provide an exception handling mechanism. Steeped in exceptions as I am, I'm having ...
31
votes
8answers
5k views

Is throwing an exception an anti-pattern here?

I just had a discussion over a design choice after a code review. I wonder what your opinions are. There's this Preferences class, which is a bucket for key-value pairs. Null values are legal (that'...
31
votes
7answers
69k views

Why doesn't “object reference not set to an instance of an object” tell us which object?

We're launching a system, and we sometimes get the famous exception NullReferenceException with the message Object reference not set to an instance of an object. However, in a method where we have ...
28
votes
7answers
1k views

Is it okay to use exceptions as tools to “catch” errors early?

I use exceptions to catch problems early. For example: public int getAverageAge(Person p1, Person p2){ if(p1 == null || p2 == null) throw new IllegalArgumentException("One or more of ...
26
votes
5answers
4k views

How to deal with checked exceptions that cannot ever be thrown

Example: foobar = new InputStreamReader(p.getInputStream(), "ISO-8859-1"); Since the encoding is hardcoded and correct, the constructor will never throw the UnsupportedEncodingException declared in ...
26
votes
12answers
1k views

What are developer's problems with helpful error messages? [closed]

It continue to astounds me that, in this day and age, products that have years of use under their belt, built by teams of professionals, still to this day - fail to provide helpful error messages to ...
26
votes
5answers
3k views

Is use of finally clause for doing work after return bad style/dangerous?

As part of writing an Iterator, I found myself writing the following piece of code (stripping error handling) public T next() { try { return next; } finally { next = fetcher.fetchNext(...
25
votes
7answers
2k views

Should a C++ program catch all exceptions and prevent exceptions from bubbling up past main()?

I was once advised that a C++ program should ultimately catch all exceptions. The reasoning given at the time was essentially that programs which allow exceptions to bubble up outside of main() enter ...
25
votes
4answers
2k views

Using assertions versus throwing exceptions?

Often when I write a functions I want to make sure the inputs to it are valid in order to detect such errors as early as possible (I believe these are called preconditions). When a precondition fails, ...
24
votes
5answers
9k views

should I throw exception from constructor?

I know I can throw exception from constructor in PHP but should I do it? For example, if a parameter's value is not as I expected it. Or should I defer throwing an exception till a method is invoked. ...
24
votes
4answers
13k views

Why shouldn't a method throw multiple types of checked exceptions?

We use SonarQube to analyse our Java code and it has this rule (set to critical): Public methods should throw at most one checked exception Using checked exceptions forces method callers to ...
23
votes
11answers
6k views

Is the 'finally' portion of a 'try … catch … finally' construct even necessary?

Some languages (such as C++ and early versions of PHP) don't support the finally part of a try ... catch ... finally construct. Is finally ever necessary? Because the code in it always runs, why ...
23
votes
2answers
1k views

Who should read Exception.Message if at all?

When designing exceptions should I write messages that a user or a developer should understand? Who should actually be the reader of exception messages? I find exception messages aren't useful at all ...